1. Field of the Invention
The present invention relates to a heat resistant polyimide based resin composition having excellent resistance to fatigue and creep, and more particularly relates to a polyimide based resin composition comprising polyaryl ether ketone and polyetherimide in addition to extremely heat resistant polyimide and having improved fatigue resistance.
2. Description of the Related Art
Many kinds of polyimides which have been conventionally developed exhibit excellent properties such as heat resistance, static mechanical properties and chemical resistance. However, conventional polyimides have been insufficient in permanence properties such as fatigue resistance and creep properties. For example, a polyetherimide having recurring structural units of the formula (A): ##STR1## has a relatively high glass transition temperature of 210.degree..about.220.degree. C. and good static mechanical strength and has been developed its uses in various fields.
The polyimide, however, is deficient in durability such as resistance to fatigue and creep, and thus it has been difficult to develop uses for parts which require durability, that is, components which are exposed to repeated high stress.
In order to solve these problems, polyimide having recurring structural units represented by the formula (B): ##STR2## has already been developed (Japanese Laid Open Patent SHO 62-236858 and 62-253655).
The polyimide has a glass transition temperature which is 30.degree..about.40.degree. C. higher than that of the polyetherimide of the formula (A) and is excellent in mechanical properties. In point of permanence properties such as fatigue resistance and creep properties, the polyimide is considerably improved as compared with the polyetherimide having recurring structural units of the formula (A). However, the improvement has been still unsatisfactory.
For the demand of a polyimide having excellent durability, polyimides having various outstanding properties, for example, a trial of alloying the polyimide having recurring structural units of the above formula (B) with polyarylether ketone having good durability has been proposed. However, a sufficiently improved polymer alloy has not yet been provided.